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-   -   pic: our octanem drive (http://www.chiefdelphi.com/forums/showthread.php?t=128935)

zinthorne 19-04-2014 03:36
pic: our octanem drive
 

cbale2000 19-04-2014 03:38
Re: pic: our octanem drive
 
Probably the first of these I've seen using 6in wheels. Seems like this would be a lot simpler than a lot of the other ones posted here too.

blaze8902 19-04-2014 10:11
Re: pic: our octanem drive
 
Umm... Isn't that a hexacanum?

orangemoore 19-04-2014 10:14
Re: pic: our octanem drive
 
Its in a class of its own.

zinthorne 19-04-2014 11:16
Re: pic: our octanem drive
 
Quote:
Originally Posted by cbale2000 (Post 1376289)
Probably the first of these I've seen using 6in wheels. Seems like this would be a lot simpler than a lot of the other ones posted here too.
I guess it would be a hexacanem, I was actually a really simple design, We went with six inch wheels so we could put a 44 tooth sprocket on for more torque. We also used 4 two stage transmissions which gave us more pushing power too.

Toa Circuit 19-04-2014 15:48
Re: pic: our octanem drive
 
Any issues with wheel speeds being different? I'd think that could be abusive on the mecanum wheels- having them running at a different speed than the traction ones. Any jitterring or efficiency losses?

zinthorne 19-04-2014 19:43
Re: pic: our octanem drive
 
Quote:
Originally Posted by Toa Circuit (Post 1376426)
Any issues with wheel speeds being different? I'd think that could be abusive on the mecanum wheels- having them running at a different speed than the traction ones. Any jitterring or efficiency losses?
Being a driver, I didn't notice any jittering or problems with wheels speeds being different. I didn't drive around the field with the traction wheels down much, I used them for pushing. I used mecanems for general driving, and the tractions for defense, and clearing robots out of our path. It takes under 1/4 second to switch, and you can shift while moving just fine, so it wasn't a problem.

Electronica1 19-04-2014 20:12
Re: pic: our octanem drive
 
Are you still able to use the different wheels as 2 different speeds, or is it only one speed (with a normal octocanum, you have smaller traction wheels so it acts as a shifter).

Alpha Beta 19-04-2014 20:13
Re: pic: our octanem drive
 
We actually had a design similar to this in our initial brain storming session. We called it sextacanum, borrowing from the Latin prefixes. It will be great for the students who proposed this idea to see it in action. We'll have to check out some of your match videos from the PNW.

Brandon Zalinsky 19-04-2014 20:42
Re: pic: our octanem drive
 
We have pretty much the exact same system on our machine, with the same mecanum wheels. There are only a few differences. First, we have a 6:1 reduction to the traction wheel. Second, the auxiliary wheels are tractioned with Velcro (works incredibly well). To address this-

Quote:
Any issues with wheel speeds being different? I'd think that could be abusive on the mecanum wheels- having them running at a different speed than the traction ones. Any jitterring or efficiency losses?
When we actuate the "drop drive", as we call it, down, it tips the bot forward so that we have the two traction wheels and the two mecanums not connected to them contacting the floor. There is then a function in code that drops the speed of the mecanum wheels to 1/6 of their normal speed to make sure that the mecanums and velcro wheels run at the same speed.

zinthorne 19-04-2014 21:54
Re: pic: our octanem drive
 
Quote:
Originally Posted by Brandon Zalinsky (Post 1376542)
We have pretty much the exact same system on our machine, with the same mecanum wheels. There are only a few differences. First, we have a 6:1 reduction to the traction wheel. Second, the auxiliary wheels are tractioned with Velcro (works incredibly well). To address this-



When we actuate the "drop drive", as we call it, down, it tips the bot forward so that we have the two traction wheels and the two mecanums not connected to them contacting the floor. There is then a function in code that drops the speed of the mecanum wheels to 1/6 of their normal speed to make sure that the mecanums and velcro wheels run at the same speed.
We used transmissions which geared it down to 8:1 and then the extra big traction wheels with the 44 tooth sprocket helped give more power too. Same as in your design, our traction wheels lifted up the back mecanems about a half an inch.
This video has some pushing, and also a great upset win in finals.
https://www.youtube.com/watch?v=WbHHUtCGc1c

This link shows the shifting very well, and the pushing ability. You can see the front end lift up about an inch or two whenever I shift. You can also see how fast it is too.

zinthorne 19-04-2014 21:56
Re: pic: our octanem drive
 
Quote:
Originally Posted by zinthorne (Post 1376595)
We used transmissions which geared it down to 8:1 and then the extra big traction wheels with the 44 tooth sprocket helped give more power too. Same as in your design, our traction wheels lifted up the back mecanems about a half an inch.
This video has some pushing, and also a great upset win in finals.
https://www.youtube.com/watch?v=WbHHUtCGc1c

This link shows the shifting very well, and the pushing ability. You can see the front end lift up about an inch or two whenever I shift. You can also see how fast it is too.
Sorry, forgot the other link, this is from the driver station, so you can see the shifting very well.
https://www.youtube.com/watch?v=m93XfLe4fj0

tStano 20-04-2014 00:31
Re: pic: our octanem drive
 
Can you strafe with 6 mecanums? How? The physics aren't working in my mind.

EricH 20-04-2014 00:48
Re: pic: our octanem drive
 
Quote:
Originally Posted by tStano (Post 1376680)
Can you strafe with 6 mecanums? How? The physics aren't working in my mind.
It looks like it's a mecanum drive with drop-down traction wheels, rather than a 6-mecanum drivetrain.

Now, I think a 6-mecanum drivetrain could work, provided that the center mecanums were matched to opposite corners--that is, the FL and the RR mecanum wheels are matched to the CL and CR mecanums, and are oriented the same way, either via chain or via programming, or some similar setup.

tStano 20-04-2014 01:02
Re: pic: our octanem drive
 
Quote:
Originally Posted by EricH (Post 1376688)
It looks like it's a mecanum drive with drop-down traction wheels, rather than a 6-mecanum drivetrain.

Now, I think a 6-mecanum drivetrain could work, provided that the center mecanums were matched to opposite corners--that is, the FL and the RR mecanum wheels are matched to the CL and CR mecanums, and are oriented the same way, either via chain or via programming, or some similar setup.
OHHHH. This robot's a square, I thought the left side of the picture was just cut off, and now it makes a whole lot more sense. Thanks!

And I think you're right, but I think it'd be a mess to get the powers ratios right, because you've got 2 wheels on the ground fighting one. The weight balance would have to be super weird, or there would need to be a lot of math with traction forces, power draw, motor controller and motor curves, and stuff so you could manipulate power ratios so the forward components cancel when you strafe(and the sideways components do when you don't).


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